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Volumes of Cones. How to work out the volume of a cone using the height and radius.

Updated on July 7, 2010

To find the volume of a cone follow these 3 simple steps:3

Step 1 First find the area of the circle at the base of cone. Do this by using the formula A = π × r².

[π = Pi = 3.142 and r = radius of the circle (the distance halfway across)]

Step 2 Multiply the answer from step 1 by the perpendicular height of the cone (the perpendicular height is the vertical height not the slanting height).

Step 3 Finally, divide your answer from step 2 by 3.

However, if you are confident with your algebra then you can use the formula:

V = 1/3 × π × r² × h

Let’s take a look at an example.

Example 1

Find the volume of this cone:

First of all let’s use the 3 steps shown above and then we shall use the formula V = 1/3 × π × r² × h

Step 1 First find the area of the circle at the base of cone. Do this by using the formula A = π × r².

A = π × r².

A = π × 3²             (since the radius of the circle is 3cm)

A = 28. 3 cm²      (rounded to 3 signifcant figures)

Step 2 Multiply the answer from step 1 by the perpendicular height of the cone (the perpendicular height is the vertical height not the slanting height).

28.3 × 8 = 226.4                 (since the perpendicular height of the cone is 8cm)

Step 3 Finally, divide your answer from step 2 by 3.

226.4 ÷ 3             

= 74.5 cm³           (rounded to 3 significant figures)

Now let’s find the volume by substituting the height and radius directly into the formula.

The radius of the cone is 3cm and the perpendicular height is 8 cm

V = 1/3 × π × r² × h

 V = 1/3 × π × 3² × 8

V = 75.4 cm³       (to 3 significant figures)

Notice that the last answer is a little more precise than the first answer.

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  • catman3000 profile image
    Author

    Mark 7 years ago from England, UK

    Thanks. I used FX Draw 3.

  • pemekwulu profile image

    pemekwulu 7 years ago from USA

    Beautiful! What software did you use in drawing the cone?